It is now generally accepted that ultraviolet (UV) radiation can be a serious health hazard. Even a limited exposure to solar radiation can cause short- and long-term skin damage, such as erythema, burns, wrinkles, lentigo (“liver spots”), skin cancers, keratotic lesions, and other cellular changes. There is a greater risk for developing such conditions for those who spend prolonged time in the sun, such as for their occupation or during recreation.
UV radiation is just one portion of the electromagnetic spectrum with wavelengths from about 100 nm and about 400 nm, and is further divided into three subregions. UV-A radiation, from about 320 nm to about 400 nm, has the longest wavelength within the UV spectrum, and consequently is the least energetic. While UV-A rays can induce skin tanning, they are liable to induce adverse changes as well, especially in the case of sensitive skin or of skin which is continually exposed to solar radiation. In particular UV-A rays cause a loss of skin elasticity and the appearance of wrinkles, leading to premature skin aging. UV-B rays have shorter wavelengths, from about 290 nm to about 320 nm, and their higher energy can cause erythema and skin burns which may be harmful. The third subgroup, UV-C has the shortest wavelengths, from about 200 nm to about 290 nm, and the highest energy. The Earth's ozone layer effectively filters much UV-C radiation from reaching the ground. Nonetheless, UV-C rays can be generated from tanning bed devices.
In addition to harming the skin, UV radiation can injure the hair, resulting in color changes (especially for color-treated hair), embrittlement, and a loss in aesthetics (e.g., shine, manageability).
One approach to help reduce or prevent UV damage is the use of sun-care products that contain one or more UV actives. Sun-care products having one or more UV actives typically are applied on the skin, scalp, lips, and/or hair before and/or during exposure to UV radiation. (These products also are applied after exposure, for example, as part of a sun exposure remedy or daily care routine.) Swimming, rainfall, or even perspiration can washoff some of the sun-care product, so that reapplication may be recommended in these situation. These products may provided in the form of creams and lotions for the skin, and recently spray products have appeared that provide user convenience and efficacy. However, the application of sun-care products to wet skin presents its own challenges.
Sun-care products, especially those that apply clear on dry skin, typically run, drip, and/or turn cloudy/white when applied to wet skin. These effects are more than just cosmetic, as they can result in inconsistent, incomplete, or variable protection from UV damage, which is the very reason for product use. Hence, products are needed that substantially resolve these drawbacks.
Related disclosures include U.S. Pat. Nos. 4,193,989; 4,254,102; 4,486,405; 4,567,038; 5,026,540; 5,204,090; 5,223,250; 5,227,153; 5,587,148; 5,929,163; 6,007,799; 6,024,942; U.S. patent application publications 2002/0111387; 2004/0166070; 2004/0247550; 2004/126,336; 2006/0051384; 2008/0014155; international patent applications WO 2005/107693 and 2011/038120; German patent application DE 10 2004 029328; 199 26 671; Japanese patent JP 5311076; and U.K. patent GB 2404588